MOSCOW — The Russian military said Wednesday it has teamed up with Turkey to conduct joint airstrikes, coordinated with Damascus, against an Islamic State group’s (I.S.) stronghold in northern Syria. It is the first acknowledgement of Russian cooperation in support of Turkey’s offensive in the area.

It is also the first incident of indirect coordination between the Turkish and the Syrian governments. Ankara has been calling for the ouster of President Bashar Assad and has supported the armed rebellion against him. Syrian officials have called Turkey’s operations on Syrian territories an “occupation.”

In a sign of a possible new ground for cooperation in the area, U.S. defense officials said Tuesday the U.S-led coalition have also carried out attacks against I.S. in the same area— al-Bab, in the province of Aleppo — at a time when Turkish troops have struggled there since November.

Lt. Gen. Sergei Rudskoi of the military’s General Staff said nine Russian warplanes and eight Turkish jets have taken part in the strikes on the outskirts of al-Bab. He said the joint airstrikes were “coordinated with the Syrian side.”

Rudskoi’s statement was the first acknowledgement of the Russian strikes in support of the Turkish offensive on al-Bab, which began in mid-November.

It highlighted an increasingly close alliance between Russia and Turkey, which last month jointly brokered a Syria truce and are working to prepare Syrian talks in Kazakhstan next week. The two nations have backed opposing sides in the nearly six-year Syrian conflict, with Moscow supporting Assad and Ankara backing his foes.

In August, Turkish troops rolled over the border to help Syrian opposition forces battle IS and halt the advance of U.S.-backed Syrian Kurdish fighters, who are also fighting the extremists. But as IS puts up a fight for al-Bab, Turkey has become bogged down in a grueling battle over the town, one of the few remaining I.S. strongholds in northern Syria.

Turkey, which for years supported the Syrian opposition drive to oust Assad, has recalibrated its priorities toward fighting Islamic State militants and thwarting Kurdish aspirations for autonomous rule along Syria’s border with Turkey. In doing so, it has also pivoted toward Russia, working with Moscow to call for a cease-fire in Syria and organize the talks scheduled for Monday, bringing the government and the opposition together.

“Today, the Russian and Turkish air force are conducting the first joint air mission to strike the IS on the outskirts of al-Bab in the province of Aleppo,” Rudskoi said at Wednesday’s briefing.

He said that Russian and Turkish aircraft struck 36 targets, which have been jointly selected by General Staffs and air force officials of the two militaries.

Rudskoi added that drones and satellites had been involved in target selection over the past two days.

Last week, the Russian and Turkish militaries signed an agreement to prevent mid-air incidents and ensure air safety during operations over Syria. “It created the basis for unprecedented joint action against international terrorist groups in Syria,” Rudskoi said.

Turkey had criticized the United States for its lack of support for the offensive in al-Bab. In December, Ankara said Russia had conducted airstrikes near al-Bab. At the time, U.S. officials said they have seen no indication of Russian-Turkish coordination, reporting only independent Russian airstrikes there.

On Tuesday, U.S. army Col. John Dorrian, a spokesman for the U.S.-led anti-I.S. coalition, said the coalition has conducted several reconnaissance missions and airstrikes in support of Turkey and the Syrian opposition fighters on the ground operating against al-Bab.

Iran, also an ally of Assad which is a co-guarantor of the cease-fire, criticized the reported Russia-Turkey aerial cooperation. Earlier this month, senior Iranian lawmaker Alaeddin Boroujaerdi said coordination with Moscow is not the same thing as coordinating with Damascus. If Ankara hadn’t sought permission from Damascus, Boroujaerdi said, it should leave “immediately.”

Meanwhile, Rudskoi criticized the U.S.-led coalition, saying its operations in Mosul have effectively caused a flood of I.S. fighters into eastern Syria.

“The actions of the U.S.-led coalition in Mosul have amounted largely to squeezing significant forces of the I.S. from Mosul into eastern part of Syria,” he said. “They have been carrying weapons, explosives and personnel to Palmyra, Deir el-Zour and al-Bab.”

Rudskoi said that the Islamic State group is preparing to blow up ancient ruins in Palmyra, shipping large amounts of explosives to the ancient city with the aim to destroy historic heritage sites there.